The present invention relates to a method and an apparatus for forming bulging portions on a metal plate by performing cold-pressing on the metal plate with a die including a die block and a punch.
A conventional fuel-cell separator includes bulging portions provided on a metal plate to form a flow passage through which gas such as hydrogen and oxygen, coolant, or the like flows. For example, Japanese Patent No. 5573511 and Japanese Laid-Open Patent Publication No. 2014-213343 disclose methods for forming a fuel-cell separator.
According to the forming method disclosed in Japanese Patent No. 5573511, as shown in FIG. 9, a die block 41 and a punch 42, which constitute a die 40, press sidewalls 512 of bulging portions 51 of a metal plate 50 while being separated from the tops 511 of the bulging portions 51.
According to the forming method disclosed in Japanese Laid-Open Patent Publication No. 2014-213343, as shown in FIG. 10A, in a first step, the die block 61 and the punch 62 of a first die 60 forms bulging portions 81 on a metal plate 80. At this time, the top 811 of each bulging portion 81 is configured to be thinner than other portions. Next, in a second step, as shown in FIG. 10B, the die block 71 and the punch 72 of a second die 70 press the sidewalls 812 of the bulging portions 81. Then, in a third step, the die block and the punch of a third die, which are not illustrated, shape the sidewalls 812 of the bulging portions 81 in a vertical direction and expand the tops 811 of the bulging portions 81.